Abnormal uterine bleeding occurs in over 25% of adolescents. Establishing normative data for menstrual bleeding would facilitate earlier diagnosis of abnormal bleeding and earlier interventions to improve health and quality of life. Current data on duration and timing from menarche to the establishment of normal menstrual cyclicity are sparse, and despite the known impact of race and obesity on timing of menarche, normative data by race and body mass index are even more limited. Advancements such as smart phones enable greater access to adolescents and decrease barriers to research on menstruation. Successful technology in this arena requires a multi-platform application (app) that allows for transfer of HIPAA-compliant patient-level information directly to researchers and demonstrates sustained patient engagement. The objective of this R21 application is to expand upon our prior work by developing a multi-platform application, and testing compliance and engagement with the app in younger adolescents with diversity in race and body weight. The rationale for this research is that development of patient-directed electronic menstrual tracking technology with immediate and seamless transition of data to researchers will enable the design of multiple longitudinal studies of menstrual bleeding patterns. The proposed work is responsive to the NICHD's call for the ?development of innovative tools and technologies to measure menstrual cycle characteristics such as bleeding, pain, and menstrual irregularity.? The specific aims of this application are: 1) develop a multi-platform menstrual tracking app to measure the degree and duration of bleeding, irregularity, location and severity of pain (dysmenorrhea), and the psychosocial impact of menses; and 2) test patient satisfaction, compliance, and sustained engagement with the app in a six-month prospective cohort study of 10-14 year-old females, and evaluate the impact of patient age, race and body mass index on these outcomes. The proposed work is innovative because our technology allows for the transfer of patient-level menstrual data to investigators on a variety of domains and our patient population includes young adolescents of diverse race and body weight. Completion of this R21 award will yield the following expected outcomes: 1) a multi-platform menstrual tracking app with high patient usability and satisfaction ratings, and 2) demonstration of the feasibility and initial sustainability of mobile electronic menstrual tracking in adolescents. These outcomes will lead to submission of an R01 application to utilize the technology herein created to perform a longitudinal assessment of race and weight-based norms of menstrual bleeding patterns during pubertal progression. The proposed work is significant because it will yield a new application of technology that can be used in multiple future research studies by our research team and others to both establish normal ranges of menstrual cycle characteristics across the age spectrum and across populations, and measure patient-reported outcomes in clinical trials of interventions for abnormal uterine bleeding.